Address the real lifetime issue of the SDK's Client by making Context.mediaProvider weak. (#4466)

This reverts commit 8d069fb74c.

ElementX/Sources/Screens/Spaces/Common/SpaceHeaderView.swift

@@ -151,14 +151,12 @@ struct SpaceHeaderMembersView: View {
 }
 
 struct SpaceHeaderView_Previews: PreviewProvider, TestablePreview {
-    static let mediaProvider = MediaProviderMock(configuration: .init())
-    
     static let spaces = makeSpaceRooms()
     
     static var previews: some View {
         VStack(spacing: 0) {
             ForEach(spaces, id: \.id) { space in
-                SpaceHeaderView(spaceRoomProxy: space, mediaProvider: mediaProvider)
+                SpaceHeaderView(spaceRoomProxy: space, mediaProvider: .mock)
             }
         }
     }

ElementX/Sources/Screens/Spaces/Common/SpaceRoomCell.swift

@@ -134,8 +134,6 @@ struct SpaceRoomCellButtonStyle: ButtonStyle {
 }
 
 struct SpaceRoomCell_Previews: PreviewProvider, TestablePreview {
-    static let mediaProvider = MediaProviderMock(configuration: .init())
-    
     static let spaces = [SpaceRoomProxyProtocol].mockSpaceList
     
     static var previews: some View {
@@ -143,7 +141,7 @@ struct SpaceRoomCell_Previews: PreviewProvider, TestablePreview {
             ForEach(spaces, id: \.id) { space in
                 SpaceRoomCell(spaceRoomProxy: space,
                               isSelected: false,
-                              mediaProvider: mediaProvider) { _ in }
+                              mediaProvider: .mock) { _ in }
             }
         }
     }

ElementX/Sources/Screens/Spaces/SpaceScreen/View/SpaceScreen.swift

@@ -78,7 +78,7 @@ struct SpaceScreen_Previews: PreviewProvider, TestablePreview {
         let viewModel = SpaceScreenViewModel(spaceRoomListProxy: spaceRoomListProxy,
                                              spaceServiceProxy: SpaceServiceProxyMock(.init()),
                                              selectedSpaceRoomPublisher: .init(nil),
-                                             mediaProvider: MediaProviderMock(configuration: .init()),
+                                             mediaProvider: .mock,
                                              userIndicatorController: UserIndicatorControllerMock())
         return viewModel
     }